Hemoglobin is Positively Associated with Bone Strength in Young Adults Entering the Military

Stress fracture incidence is high during initial military training (IMT) with 2-6% of male and 8-21% of female recruits sustaining fractures. Identification and mitigation of risk factors is critical in efforts to preserve the health of military trainees and decrease injury costs. Prior reports indicate that iron deficiency anemia (IDA) is a risk factor for stress fracture in military recruits. The current study aimed to determine whether hemoglobin (Hgb), the iron-containing oxygen transport protein, was associated with bone strength in young adults entering the military. Bone density, geometry, and strength were measured using peripheral quantitative computed tomography at the 4, 14, and 66% tibia sites , and fasted blood samples collected in 165 (n=90 female [Age = 21.4 ± 2.6 y; BMI=23.9 ± 2.7], n=75 male [Age=20.0 ± 2.6 y, BMI=25.1 ± 3.3]) recruits prior to IMT. Hgb was not associated with any trabecular bone parameter including bone strength at the 4% site (r=0.11, p=0.19). However, Hgb was positively correlated with cortical content (r=0.17, p=0.04) at the 14% site and polar stress-strain index, a surrogate measure of bone strength, at the 66% site (r=0.17, p=0.05) even when controlling for sex and body weight. These findings support a potential role of iron status in cortical bone health suggesting it may be involved in suppression of bone resorption or promotion of bone formation, and provides the basis for future research exploring the effects of iron on bone metabolism in young adults. Research supported by: ORISE and USAMRMC.